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finite element for soil and rock analyses

15‐JUNE‐2007

Plaxis Vietnam Seminar No

Title

1

The Plaxis Approach‐ Geotechnics, Deep  Excavation, Foundations and  etc

2

Soil Models and Structural Elements

3

Geometry, Model Space, Mesh and Initial Stresses

4

Notes on usage of Plaxis Codes on the modelling of  Excavations and Tunnels

Time

F I N I T E E L E M E N T C O D E F O R S O I L A N D R O C K A N A LY S E S

Vietnam 2008

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finite element for soil and rock analyses

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finite element code for soil and rock analyses

PLAXIS SEMINAR KUCHING 2008 Malaysia

C Computational Geomechanics in Routine Geotechnical Analysis  t ti l G h i  i  R ti  G t h i l A l i  

THE PLAXIS APPROACH VISUALISE ANALYSE OPTIMISE > T H E   W A Y   F O R W A R D

Contributed

William W.L. CHEANG Regional Technical Manager PlaxisAsia (Plaxis BV)

Ir. Erwin BEERNINK Ir. Dennis WATERMAN Dr. Erick SEPTANIKA Dr. Ronald BRINKGREVE Dr. Siew Wei LEE Dr. Andy PICKLES Prof. Pieter .A.VERMEER PROF. Yasser EL. MOSSALLAMY

L A XI S P R O F E S S I O N A L v e r s i o n 8 . 5 - P L A XF L O W v e r s i o n 1 . 5 - D Y N A M I C S m o d u l e - 3 - D F O U N D A T I O N v e r s i o n 2 . 0 – 3 - D T U N N E L v e r s i o n 2 . 0 – 3 - D G E O T H E R M I E v e r s i o n 1 .

SEMINAR 1. GEOTECHNICAL ENGINEERING 2. GEOTECHNICAL ANALYSIS G O C C SS 3. MODELLING OF SOIL‐STRUCTURE 

INTERACTION PROBLEMS WITH PLAXIS 4. REAL CASE HISTORIES 5. CONCLUSIONS

Vietnam 2008

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finite element for soil and rock analyses

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finite element code for soil and rock analyses

1. 2. 3. 4. 5.

TUNNELLLING EXCAVATION FOUNDATIONS LAND RECLAMATIONS SLOPE (EMBANKMENT) STABILITY  AND   REINFORCEMENT

1.GEOTECHNICAL ENGINEERING 1 GEOTECHNICAL ENGINEERING

TUNNELLING N E W A U S T R I A N T U N N E L L I NG

SHIELD TUNNELLING

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finite element for soil and rock analyses

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The design of sequential excavations depends on the quality of the ground The smaller the excavated area the smaller the settlements.

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finite element for soil and rock analyses

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Case study: Heinenoord tunnel near Rotterdam

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finite element for soil and rock analyses

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EXCAVATIONS

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finite element for soil and rock analyses

15‐JUNE‐2007

FOUNDATIONS

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PILED RAFTS FOUNDATIONS

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finite element for soil and rock analyses

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LAND RECLAMATION

Deformed mesh at completion of staged reclamation (exaggerated scale)

Sandfill W.T.

PVD

Soft CLAY Sandy SILT

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SEMINAR 1. GEOTECHNICAL ENGINEERING 2. GEOTECHNICAL ANALYSIS G O C C SS 3. MODELLING OF SOIL‐STRUCTURE 

INTERACTION PROBLEMS WITH PLAXIS 4. REAL CASE HISTORIES 5. CONCLUSIONS

Vietnam 2008

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finite element for soil and rock analyses

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finite element code for soil and rock analyses

2.GEOTECHNICAL ANALYSIS 2 GEOTECHNICAL ANALYSIS

2.GEOTECHNICAL ANALYSIS

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Vietnam 2008

GEOMETRY SPACE 1.

2‐D Plane Strain Space

2.

Axi‐symmetric space

3.

3‐D Space

30 m

45 m 45 m

8m

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finite element for soil and rock analyses

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AXI-SYMMETRY AND NON AXI-SYMMETRY

AX I - S YM M E T RY

N O T AX I - S YM M E T RY

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SEMINAR 1. GEOTECHNICAL ENGINEERING 2. GEOTECHNICAL ANALYSIS G O C C SS 3. MODELLING OF SOIL‐STRUCTURE 

INTERACTION PROBLEMS WITH PLAXIS 4. REAL CASE HISTORIES 5. CONCLUSIONS

Vietnam 2008

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finite element for soil and rock analyses

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finite element code for soil and rock analyses

Plaxis Finite Element Codes

3.SOIL‐STRUCTURE INTERACTION 3 SOIL STRUCTURE INTERACTION

3.FINITE ELEMENT ANALYSIS WITH PLAXIS

“ R E A L I T Y O R V I RT U A L D R E A M ? ”

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finite element for soil and rock analyses

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F I N I T E E L E M E N T C O D E F O R S O I L A N D R O C K A N A LY S E S

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PLAXIS FINITE ELEMENT CODES Overview of current products: CURRENT SUITE OF PROGRAMS

+ ADD‐ONS MODULES

Plaxis Version 8.6

Dynamics

Plaxis PlaxFlow Version 1.5

(VI Package)

Plaxis 3D Tunnel Version 2.2 Plaxis 3D Foundation Version 2.1

P L A X I S V 8

Vietnam 2008

PLAXIS SEMINAR‐HO CHI MINH

PLAXFLOW

3D TUNNEL

3D FOUNDATION

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finite element for soil and rock analyses

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PLAXIS PROGRAMS AND ANALYSIS TYPE Analysis Type

Product (Code)

2D Analysis  Stress ‐Deformation

3D Analysis

Plaxis Professional Version 8.6

1.Stress –Deformation 2.Dynamic Problems

Combine Plaxis Professional Version 8.6 +  Dynamics module

11.Stress‐Deformation Stress‐Deformation 2.Transient Flow Problems

Combine Plaxis Professional Version 8.6 +  Version 8 6 +  PlaxFlow

Tunnels* Excavation Slope Reinforced Wall

Plaxis 3D Tunnel Version 2.4

Foundations* Piled Foundations Piled Raft Foundations l d f d Excavations

Plaxis 3D Foundation Version 2.1

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PLAXIS SEMINAR‐HO CHI MINH

Version 4

Version 5

Version 6

Version 7

Dynamics

3D Tunnel

Version 8

PlaxFlow

3D Found v11

3D Found v1.6

3D Found v2.0

2D  Version 9  9

19 991

19 993

19 995

19 998

20 000

20 001

20 002 20 003

20 004

20 005

20 007

20 008

Version 3 19 990

19 989

19 987

Version 1

Version 2

PLAXIS DEVELOPMENT TIME-LINE

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finite element for soil and rock analyses

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PROGRAMS (CODES): 2D AND 3D

PLAXIS 2D

PLAXIS 3D

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PLAXIS PROFESSIONAL v8.6

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finite element for soil and rock analyses

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PLAXIS V8

Excavations

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PLAXIS V8

Soil reinforcement

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finite element for soil and rock analyses

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PLAXIS V8

Tunnels

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PLAXIS PROFESSIONAL VERSION 8.5

MOVIE 1

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finite element for soil and rock analyses

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PLAXIS PLAXFLOW v1.5

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PLAXFLOW

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finite element for soil and rock analyses

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PLAXFLOW + PLAXIS 8

Deformations

Ground waterheads

MOVIE 1

RAIN WATER INFILTRATION ON PARTIALLY SATURATED SLOPE Vietnam 2008

MOVIE 2

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DYNAMICS MODULE

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finite element for soil and rock analyses

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PLAXIS DYNAMICS MODULE For vibrations and earthquake simulation 1. 2. 3.

Single‐source vibrations Earthquake analysis Absorbing boundaries

S TRON G MOTION  IN PUT FROM S MC

MOVIE

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PLAXIS 3D TUNNEL v2.2

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finite element for soil and rock analyses

15‐JUNE‐2007

PLAXIS 3D TUNNEL

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PLAXIS 3D TUNNEL APPLICATIONS MODELLING OF SHIELD TUNNELLING PROCESS

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finite element for soil and rock analyses

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PLAXIS 3D TUNNEL APPLICATIONS SIMULATION OF SOIL‐STRUCTURE INTERACTION: EFFECT OF TUNNELLING ON STRUCTURE

MOVIE

47

Vietnam 2008

PLAXIS 3D TUNNEL APPLICATIONS TWIN TUNNELS

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finite element for soil and rock analyses

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PLAXIS 3D FOUNDATION v2.1

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PLAXIS 3D FOUNDATION: PILES

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finite element for soil and rock analyses

15‐JUNE‐2007

PLAXIS 3D FOUNDATION: PILED FOUNDATIONS

51

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STRUCTURE ON SLOPE

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finite element for soil and rock analyses

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PLAXIS 3D FOUNDATION: PIERS

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COMPLEX SOIL STRUCTURE INTERACTION MODEL

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finite element for soil and rock analyses

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MULTI-SUCTION BUCKETS (OFFSHORE)

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TANK ON PILED RAFT FOUNDATION

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finite element for soil and rock analyses

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COMPLEX SOIL STRUCTURE INTERACTION PROBLEMS

MOVIE

E X C AVAT I O N S

MOVIE

COFFERDAM

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DEVELOPMENTS

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finite element for soil and rock analyses

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RECENT DEVELOPMENTS – 3D FOUNDATION Plaxis 3D Foundation Version 2 ƒ Embedded piles ƒ Ground anchors ƒ Phi‐c reduction ƒ Simulation of soil tests ƒ Small‐strain stiffness (HS‐small) ƒ User‐defined soil models ƒ Grouping of elements ƒ New Output program N  O t t 

4

13 5

101

15

14 6 11

102

10 1

7 2

10 3

12 9 8 3

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finite element for soil and rock analyses

15‐JUNE‐2007

QUAY WALLS

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ANCHORING OF QUAY WALLS

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finite element for soil and rock analyses

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MICROPILES

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Constitutive Soil Models Linear Elastic 2. Linear Elastic Perfectly Plastic  :  • Mohr‐Coulomb 3. Isotropic Hardening Models:  • Hardening Soil Model ( Failure Criterion, MC, Lade & Matsuoka‐ Nakai) • Double Hardening • Cam‐Clay Class of models (Soft‐soil  & Soft soil creep) 1.

SSome other elements that may be important: th l t th t b i t t • Anisotropy • Small‐strain stiffness effects • Cyclic effects

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finite element for soil and rock analyses

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SEMINAR 1. GEOTECHNICAL ENGINEERING 2. GEOTECHNICAL ANALYSIS G O C C SS 3. MODELLING OF SOIL‐STRUCTURE 

INTERACTION PROBLEMS WITH PLAXIS 4. REAL CASE HISTORIES 5. CONCLUSIONS

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finite element code for soil and rock analyses

2‐D MODELLING OF EXCAVATIONS 3‐D MODELLING OF EXCAVATIONS 3‐D PILED RAFT FOUNDATIONS

4 REAL CASE HISTORIES 4. REAL CASE HISTORIES

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finite element for soil and rock analyses

15‐JUNE‐2007

finite element code for soil and rock analyses

OVAL COFFERDAM NICOLL HIGHWAY INVESTIGATION EFFECT OF  TENSION PILES  EFFECT OF PASSIVE PILES

APPLIED 1: EXCAVATION APPLIED 1  EXCAVATION

Oval Cofferdam Structure Details Plan View

Cross Section 32m

32m

24m

27m

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finite element for soil and rock analyses

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Oval Cofferdam Details • Excavation for a pumping station • Ground conditions: Fill, Clay, Alluvium, CDG, Rock • Oval cofferdam size 24 m × 32 m (plan view) • 27 m deep excavation in 6 stages • DWall thickness 1.2 m • Ring beams size 0.8 m × 1.8 m • Original Oi i ld design i used d 2D modelling d lli • Struts size 305 × 406 × 287 (necessary?) • 3D modelling explores early struts removal Vietnam 2008

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Designer’s Original Analysis in 2D

• Model plane strain excavation • No consideration of hoop force in ring DWalls and ring beams Vietnam 2008

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finite element for soil and rock analyses

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3D Analysis Plaxis 3D Foundation

Mesh size 200×170×40m

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Retaining System for Oval Cofferdam Volume element

Spring

Deformation (150x)

Pile with Shell

Vietnam 2008

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finite element for soil and rock analyses

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Stress in Ring Beams & Force in Struts Mean stress in ring beams

Strut Forces

(kPa) Layer

2D (kN)

3D (kN)

1st strut str t

2064

1083 (52%)

2nd strut

4200

1577 (38%)

3rd strut

4552

1584 (35%)

4th strut

7856

1503 (19%)

5th strut

6784

2285 (34%)

6th strut

5848

2271 (39%)

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Comparison of 2D & 3D Deformations Parameter

2D

3D

Max. ground settlement

31 mm

10 mm

Max. wall deflection

64 mm

25 mm

• Bottom-up construction on-going • Field measurements close to 3D predictions

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finite element for soil and rock analyses

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Check for One Strut Failure • BS8002:1994, Cl. 4.5.2.2.1 states The design should also accommodate the possible failure of an individual strut tie rod or anchor. • CIRIA C580, Cl. 5.6.3, Accidental Load Case considers … loss of a prop (partial support) to the wall, … • Ensure failure of one strut would not lead to collapse • Removal of one strut in 2D analysis 1. removes a whole row of struts into-the-plane into the plane 2. does not consider redistribution of soil stresses and strut forces in 3D space • Carry out 3D analysis using 3D Tunnel/Foundation 75

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Check for One Strut Failure Plaxis 3D Tunnel Increase in adjacent strut forces due to one strut removal

One strut removed

30m

18% 47% 18% 5% 16%

17% 6%

One strut removed • Strut vertical spacing 3m, horizontal spacing 4m

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finite element for soil and rock analyses

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Check for One Strut Failure Wall bending moment contours

Increase in wall horizontal deflection contours

Strut removed (10mm increase)

45m

1400 kNm/m increase

32m 77

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Modelling of a Gap in Wall

Wall panel

G Gap

Wall panel

Gap in wall • Gap in wall for utility crossing • Modelled by PLAXIS 3D Tunnel

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finite element for soil and rock analyses

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Modelling of a Gap in Wall Wall deflection contours Wall

Wall

Grouted slab

160mm deflection Gap below final exc. Panel 0.8m thk

Gap infilled by grout

Panel 1.0m thk

Panel 0.8m thk

• Panel filling gap as excavating downward

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Idealisation of Individual Piles as Walls Singapore +103

DWall +96

1.0mØ pile (6.5m c/c) 24m

+81

8.5m

1.8mØ pile (13m c/c)

12.5m

DWall • 22m deep top down exc. in soft clay • 1.0 and 1.8m Ø pile installed within cofferdam

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PLAXIS SEMINAR‐HO CHI MINH

+50 +45

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finite element for soil and rock analyses

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3D Modelling of Individual Piles PLAXIS 3D Foundation

DWall

Slab

+50m

DWall

1.0mØ pile (+50m) 1.8mØ pile (+45m)

1.8mØ Models half geometry

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Comparison of Wall Deflection 3D

100

100

95

95

90

90

85

85

80

80 mRL

105

75

60

Wall horizontal disp. (m)

0.055

0.050

0.045

0.040

0.035

0.030

0.025

0.055

0.050

0.045

0.040

0.035

0.030

0.025

0.020

0.010

0.005

45 0.000

50

45

0.020

55

50

0.015

55

65

0.010

60

0.005

65

75 70

2D predicts smaller DWall deflections, as soil is not allowed to flow between piles

0.000

70

0.015

mRL

2D 105

Wall horizontal disp. (m)

Diaphragm wall deflection

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finite element for soil and rock analyses

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Comparison of Tension Force in Piles 1.0m Ø pile at 6.5m c/c

1.8m Ø pile at 13m c/c 100

100

95

95

3D gives 3000 kN

90 85

70 65

Compression/tension force in pile (kN)

20000

2D gives 20000 kN 15000

45 20000

50

45 15000

50 10000

55

5000

60

55

0

60

10000

65

3D gives 1400 kN

75

5000

70

80

0

75

Level (mRL)

2D gives 10000 kN

80

-5000

Level (mRL)

85

-5000

90

Compression/tension force in pile (kN)

• Tension force (+ve) in piles due to ground heave in cofferdam

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Notes on Individual Piles as Walls • Widely spaced individual piles within cofferdam modelled as continuous walls in 2D analysis would predict: 1 Smaller deflection of retaining wall. 1. wall Continuous wall does not allow flow of soil between piles, i.e. wall too rigid. 2. Larger tension force in the continuous wall. Larger surface area of wall for mobilisation of shaft resistance. • Consequences might be: 1. under-design of retaining wall 2. unnecessary sleeving/coating of individual piles in cofferdam • Discrepancy between 2D and 3D prediction increases with the increase of individual piles spacing into-the-plane.

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finite element for soil and rock analyses

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Effect of Excavation on Piles Macau

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Effect of Excavation on Piles •

Piles for supporting high-rise

“Dido” pile external dia. 0.6 m, internal dia. 0.3 m

Pile spacing 3 - 8 m, length ~ 45 m

Ground conditions: fill, soft clay, stiff soil

Excavation 3 - 4 m for construction of pile caps

3D analysis to investigate

1. effect of excavation on pile deflection 2. contribution of piles to FOS of excavation slope

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finite element for soil and rock analyses

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3D Analysis Individual piles

65m

8m • Individual piles modelled by “plate” element

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Deformation of Excavation Piles resist deformation

20x

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PLAXIS SEMINAR‐HO CHI MINH

• Localised deformation around piles

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finite element for soil and rock analyses

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Deformation of Piles 200 C B A

180

Soft soil

Stiff soil

A

B

C

Pile head deflection (mm)

160 140 120 100 80 60 40 20

• Measured pile deflection: order of 100 mm

0 Exc to +2.5

Exc to +1.3

Exc to +0.8

Back exc Back exc to +2.5 to +4.5

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Phi-c Reduction to Determine FOS Remember to input moment capacity of piles Mp!

Plastic hinge

Vietnam 2008

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finite element for soil and rock analyses

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FOS for Different Excavation Depths 2.40 2.20

piles

FOS

2.00 1.80 1.60 1.40

no piles

1.20 1.00 Exc to +2.5

Exc to +1.3

Exc to +0.8

Back exc to +2.5

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Back exc to +4.5

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finite element code for soil and rock analyses

1.EFFECT OF BARRET PILES ON ADJACENT INFRASTRUCTURE 2.PILED FOUNDATION ANALYSIS 3. CALIBRATION TEST: NUMERICAL AND CENTRIFUGE

APPLIED 2 FOUNDATIONS APPLIED 2:FOUNDATIONS

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finite element for soil and rock analyses

15‐JUNE‐2007

Foundation System for a High-rise Singapore

• High-rise above an existing tunnel

(12m) Tunnel

• Barrettes straddle tunnel • Barrettes 1.5m thick, 100 m deep • Tunnel settlement criteria 15 mm

High-rise footprint

• Ground conditions: 35 m soft clay underlain by stiff soil • 2D & 3D analyses to optimise barrette geometries

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Geometry of Existing Tunnel

Bored pile • Supported by three row of bored piles 1.2 - 1.5m Ø @ 4 - 8 m c/c • Bored piles ~60 m long • Tunnel T l width idth 12 m, h height i ht 6 m, floor/wall thickness 1 m • Tunnel 5 m below ground surface

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finite element for soil and rock analyses

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2D Analysis High-rise loading

tunnel

Barrette

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Limitations of 2D Analysis •

Line load applied on barrettes is uniform into-the-plane

In real situation

1 line 1. li lload d iis applied li d within ithi th the b building ildi area 2. barrette section further away from building boundary helps shed load through skin friction • Existing bored piles supporting the tunnel are modelled as “wall” into-the-plane • Changes of axial force in existing piles may not be reliably predicted • Cannot give settlement profile of the tunnel into-the-plane (for structural calculation of tunnel deflection/distortion)

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finite element for soil and rock analyses

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3D Analysis Plaxis 3D Foundation - half problem modelled Pile-soil area

60m

Line load on barrette Symmetry plane

Tunnel 152m

160m

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Structural Items in 3D Analysis Tunnel

Volume element: barrettes, transfer beams & piles

Line load on barrette

“Floor” element: tunnel roof and floor slab “Wall” element: tunnel walls Interface element: on barrettes, transfer beams, wall & piles

Piles

Transfer beam

Barrette (100 m) Building load (equivalent raft foundation) Vietnam 2008

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3D Analysis Results Settlement of tunnel Settlement

Deformation 500x

roof

floor

Settlement of tunnel

walls 99

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3D Analysis Results Longitudinal Settlement Profile of Tunnel

Increase of Axial Force in Tunnel Piles

Distance in longitudinal direction of tunnel (m)

95 West pile

90

0

20

30

40

50

60

West side East side

East pile

80 75 70 65 60

Soft soil

55

Stiff soil

50

Settlement (m)

Elevation (+mRL)

10

Middle pile

85

45 40 35 Increase of axial force in pile (kN)

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Summary of Barrette Foundation Analysis • 3D analyses predict smaller tunnel settlement than 2D, reduction by 3 - 5 times • 3D analyses model better 1. stress bulb of building load 2. load shedding through skin friction in barrettes 3. increase of axial force in tunnel piles 4. longitudinal settlement profile of tunnel

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103

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105

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finite element for soil and rock analyses

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finite element code for soil and rock analyses

1.SETTLEMENT OF STRUCTURE DUE TO CONSOLIDATING GROUND & THE  EFFECT OF NEGATIVE SKIN FRICTION 2.EFFECT OF EMBANKMENT ON SERVICE PIPE

APPLIED 3:DEFORMATION  APPLIED 3 DEFORMATION  ANALYSIS

Settlement at a Depot Site Taiwan

Plan view area 280m×130m • Two-storey depot supported by 0.5m Ø driven piles in alternating layers of clay and sand, sand with pile toes founded in sand • Consolidation settlement occurring due to placement of 2-3m surface fill onto near surface clay layer • Concern for negative skin friction induced on pile groups

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SETTLEMENT AT A DEPOT SITE Point load 1.25m 2.5m +21.5 mRL

FILL

+19.5 mRL

Model ¼ pile group Upper CLAY +10 mRL

SAND

37m

PLAXIS 3D Foundation +0 mRL

16m

Lower CLAY

0.5m dia. pile

-10 mRL

Lower SAND -15 mRL

15m

15m

Toe +5.5 mRL

10 9

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Settlement at a Depot Site Excess pwp contours •

Modelling sequences

1. Initial equilibrium 2. 2-3 m Fill placement (epwp) Clay

3. Install pile cap and piles 4. Apply building load 600 kN to ¼ of pile cap (epwp) 5. Consolidation (dissipation of epwp)

Clay

Dissipation of epwp

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Settlement at a Depot Site Consolidation settlement 130mm 100mm

Pile toe

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SETTLEMENT AT A DEPOT SITE

Time (Day) 0

100

200

300

400

500

600

700

800

900

1000

0.000 F 29 F-29

-0.020

F 30 F-30

F 31 F-31

F 32 F-32

Hand calc.

Settlement (m)

-0.040 -0.060 -0.080

PLAXIS (kclay=1×10-8 m/s)

-0.100 -0.120 -0.140

6/5/04

25/4/06

-0.160

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finite element for soil and rock analyses

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Settlement at a Depot Site Axial force down the corner pile (kN) 0

50 100 150 200 250 300 350 400 450 500 550 600 650 700

22

NSF: Negative skin friction 20

metre Reduced Level m

18

Bldg. load

16

NSF 14 12 10 8

Bldg. load + consolidation

6 4

113

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8. Lateral Movement of Buried Service Pipe Service pipe Embankment

Australia

Service pipe

15m Cone

Cone

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Lateral Movement of Buried Service Pipe • 10 m high embankments and 18 m high cone to be built adjacent to an existing service pipe • Service S i pipe i 0 0.4 4 m Ø and d buried b i d1md deep • Loading from embankments and cone may deform the pipe laterally • Ground conditions: fill, soft clay, stiff clay, residual soil • 3D analysis to predict the deformation magnitude and profile of the pipe

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3D Analysis Plaxis 3D Foundation Embankment load

Alignment of buried pipe

35m

Cone load

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3D Analysis Results Deformation at Depth 1 m Below Ground Surface (50x) Deformed Pipe

Pipe modelled by “beam” element

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3D Analysis Results

Longitudinal distance (m)_

• A simple 3D loading scenario modelled by 3DF • Model the soil-structure i t interaction ti effect ff t

0 20 40

0.005

0.000

-0.005

-0.010

-0.015

-0.020

-0.025

-0.030

Lateral movement of pipe (m)

Emb.

60

• Give pipe deflection, shear force & bending moment in 3D

80 100

Cone

120 140 160 180 200

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finite element for soil and rock analyses

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SEMINAR 1. GEOTECHNICAL ENGINEERING 2. GEOTECHNICAL ANALYSIS G O C C SS 3. MODELLING OF SOIL‐STRUCTURE 

INTERACTION PROBLEMS WITH PLAXIS 4. REAL CASE HISTORIES 5. CONCLUSIONS

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General Notes for FE Analysis • Soil input parameters and modelling techniques continually refined as more field data is available • A series of sensitivity analyses are necessary to cover possible field scenarios • Use of numerical modelling in practice requires: 1. A good knowledge of soil mechanics and finite element/difference principles 2. An understanding of the programme/model limitations 3. Careful checking of numerical results by competent engineers

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References Breth, H. and Chambosse, G. (1975). Settlement behaviour of buildings above subway tunnels in Frankfurt clay. Proc. Conf.  Settlement of Structures, Cambridge, April 1974, London: Pentech Press, 329 ‐ 336. Boscardin, M. D. and Cording, E. J. (1989). Building response to excavation‐induced settlement, ASCE, J. Geotech. Engrg., 115(2),  22 ‐28.    CIRIA (2003). Embedded retaining walls ‐ guidance for economic design. Construction Industry Research and Information  Association, Report C580.  Davies, R. V. and Henkel, D. J. (1980). Geotechnical problems associated with the construction of Charter Station, Hong Kong. Proc. of the Conf. on Mass Transportation in Asia, Hong Kong, paper J3, 31 p. Dickin, E. A. and Nazir, R. (1999). Moment‐carrying capacity of short pile foundations in cohesionless soil. J. Geotech. & Geoenv.  Engrg. ASCE, 125(1), 1‐10.    Franzius, J. N., Potts, D. M. and Burland, J. B. (2006). The response of surface structures to tunnel construction. Geotechnical Engineering, Proc. of ICE, 159(1), 3‐17. Morton, K., Leonard, M. S. M. and Carter, R. W. (1980). Building settlements and ground movements associated with  construction of two stations of the modified initial system of the Mass Transit Railway, Hong Kong. Proc. of 2nd Int. Conf. on  Ground Movements and Structures, Cardiff, UK, 708‐802; 946‐947, Discussion (published under the title Ground Movement  and Structures, Geddes, J. D., eds., Pentech, London, 1981).  Morton, K., Cater, R. W. and Linney, L. (1980). Observed settlements of buildings adjacent to stations constructed for the  modified initial system of the Mass Transit Railway, Hong Kong. Proc. of 6th Southeast Asian Conf. on Soil Engineering,  Taipei, 415‐429. Prasad, Y. V. S. N. and Narasimha Rao, S. (1994). Experimental studies on foundations of compliant structures – I. under static  loading. Ocean Engineering, 21(1), 1‐13. PLAXIS (2002). Users forum – beam to pile properties. PLAXIS Bulletin, June, 2002, p.22,  http://www.plaxis.com/upload/bulletins/12%20PLAXIS%20Bulletin.pdf. 

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Thank you

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